Module Name: src
Committed By: maxv
Date: Tue Apr 17 09:06:33 UTC 2018
Modified Files:
src/sys/netipsec: ipsec_mbuf.c
Log Message:
Fix a pretty bad mistake, that has always been there.
m_adj(m1, -(m1->m_len - roff));
if (m1 != m)
m->m_pkthdr.len -= (m1->m_len - roff);
This is wrong: m_adj will modify m1->m_len, so we're using a wrong value
when manually adjusting m->m_pkthdr.len.
Because of that, it is possible to exploit the attack I described in
uipc_mbuf.c::rev1.182. The exploit is more complicated, but works 100%
reliably.
To generate a diff of this commit:
cvs rdiff -u -r1.23 -r1.24 src/sys/netipsec/ipsec_mbuf.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/netipsec/ipsec_mbuf.c
diff -u src/sys/netipsec/ipsec_mbuf.c:1.23 src/sys/netipsec/ipsec_mbuf.c:1.24
--- src/sys/netipsec/ipsec_mbuf.c:1.23 Tue Apr 17 06:23:30 2018
+++ src/sys/netipsec/ipsec_mbuf.c Tue Apr 17 09:06:33 2018
@@ -1,4 +1,4 @@
-/* $NetBSD: ipsec_mbuf.c,v 1.23 2018/04/17 06:23:30 maxv Exp $ */
+/* $NetBSD: ipsec_mbuf.c,v 1.24 2018/04/17 09:06:33 maxv Exp $ */
/*
* Copyright (c) 2002, 2003 Sam Leffler, Errno Consulting
@@ -29,7 +29,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ipsec_mbuf.c,v 1.23 2018/04/17 06:23:30 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ipsec_mbuf.c,v 1.24 2018/04/17 09:06:33 maxv Exp $");
/*
* IPsec-specific mbuf routines.
@@ -404,6 +404,7 @@ m_striphdr(struct mbuf *m, int skip, int
m->m_pkthdr.len -= hlen;
} else if (roff + hlen >= m1->m_len) {
struct mbuf *mo;
+ int adjlen;
/*
* Part or all of the header is at the end of this mbuf,
@@ -412,11 +413,13 @@ m_striphdr(struct mbuf *m, int skip, int
*/
IPSEC_STATINC(IPSEC_STAT_INPUT_END);
if (roff + hlen > m1->m_len) {
+ adjlen = roff + hlen - m1->m_len;
+
/* Adjust the next mbuf by the remainder */
- m_adj(m1->m_next, roff + hlen - m1->m_len);
+ m_adj(m1->m_next, adjlen);
/* The second mbuf is guaranteed not to have a pkthdr... */
- m->m_pkthdr.len -= (roff + hlen - m1->m_len);
+ m->m_pkthdr.len -= adjlen;
}
/* Now, let's unlink the mbuf chain for a second...*/
@@ -424,9 +427,10 @@ m_striphdr(struct mbuf *m, int skip, int
m1->m_next = NULL;
/* ...and trim the end of the first part of the chain...sick */
- m_adj(m1, -(m1->m_len - roff));
+ adjlen = m1->m_len - roff;
+ m_adj(m1, -adjlen);
if (m1 != m)
- m->m_pkthdr.len -= (m1->m_len - roff);
+ m->m_pkthdr.len -= adjlen;
/* Finally, let's relink */
m1->m_next = mo;
